PTMEG is frequently manufactured by polymerizing tetrahydrofuran (THF) in the presence of a fluorosulfonic acid catalyst. A major use of PTMEG is as a component of certain polyester elastomers. Some of these elastomers are the reaction products of, among other things, terephthalic acid (TPA) and PTMEG. When one reacts TPA with PTMEG prepared in the presence of fluorosulfonic acid, undesirable amounts of HF can be generated. In order to reduce HF evolution in the reaction with TPA, it is necessary to use a PTMEG which has a low concentration of fluoride.
U.S. Pat. No. 4,371,713 discloses a process for manufacturing PTMEG comprising (A) polymerizing THF in the presence of fluorosulfuric acid, (B) adding water or an aqueous solution of an alkaline material to the polymerization product and heating that system under strongly acidic conditions to hydrolyze the polymerization product. The alkaline material is preferably the hydroxide or oxide of an alkali metal, but the hydroxide or oxide of an alkaline earth metal or ammonia may be used. The hydrolysis temperature is preferably between 50.degree. C. and 150.degree. C. If the temperature exceeds 150.degree. C., decomposition or deterioration of the PTMEG is disclosed as tending to take place, and the depolymerizing action of sulfuric acid and hydrofluoric acid is intensified. The hydrolysis treatment time is usually 1 to 10 hours.
U.S. Pat. No. 3,358,042 discloses a process for recovering from an aqueous acidic solution PTMEG which had been produced via a catalytic polymerization of THF (the preferred catalysts are hydrofluoric and sulfuric acids). Polymerization was terminated by the addition of water, and the polymerization termination products, i.e., PTMEG, THF, catalyst and water, were steam-distilled until they reach a temperature of 95.degree. C., so that the unreacted THF was removed therefrom. A water-immiscible polymer solvent was added to the mixture produced by steam distillation; i.e., PTMEG, catalyst and water. The mixture of PTMEG, solvent, catalyst and some water separate into a PTMEG-solvent phase and an aqueous phase. A neutralizer, preferably calcium hydroxide, calcium carbonate or mixtures of the two, is added to the solvent phase in a quantity which is in stoichiometric excess of the acid remaining in the polymer. The uncombined water and suspended solids are then removed from the PTMEG-solvent mixture.
U.S. Pat. No. 2,751,419 discloses a process for the purification of PTMEG which had been produced via polymerization of THF in the presence of fluorosulfonic acid. The resulting sulfate esters are converted to PTMEG by a hydrolysis reaction accomplished by drowning the reaction mass in hot water under vigorous agitation or by continuous co-current drowning in a turbannular flow tube with steam as a propellant. Unreacted THF is removed from the hydrolyzed reaction mass by steam stripping, the maximum stripping temperature is 100.degree. C. The THF-stripped hydrolyzed reaction mass is washed with water, preferably in a continuous countercurrent fashion and at a water to PTMEG ratio between 1:1 to 10:1, to remove a major portion of the HF and H.sub.2 SO.sub.4. The remaining portion of HF and H.sub.2 SO.sub.4 is neutralized by mixing the mass with an aqueous slurry of calcium hydroxide. The slurry, containing 5-15% calcium hydroxide, is mixed with the mass at a ratio of about 0.25 to 5.0 parts (preferably one part) Ca(OH).sub.2 to 100 parts PTMEG. The slurry-mass mixture temperature is approximately 80.degree. C. The neutralized mass is filtered to remove the calcium hydroxide and other calcium salts. The residual water in the PTMEG is removed by evaporation, and the evaporation temperature is a maximum of 145.degree. C.